Archived from groups: alt.comp.hardware.homebuilt (
More info?)
DVD-RAM negatives...
o High cost
---- notably more than DVD+/-R media
o Fussy cartridge basis for best protection
---- you lose rewrite usage & longevity out of the cartridge
---- discs can be returned to a cartridge quite easily however
---- very few writers available that take media in cartridge directly
o Snail
---- realise how long it will take to backup to one side
---- for double-sided media you have to turn the disk over
---- slower than Magneto Optical for example
DVD-RAM positives...
o Phase change media
---- akin to Magneto Optical media in this respect
---- both magnetism & temperature are required to change data
---- basically heat material above Curie point & "flip the bit"
o Rugged cartridges
---- like Magneto Optical media, robust, shuttered etc
---- protect the media (and drive lens/laser etc) from damage, dust etc
o Higher level of error correction
---- DVD+/-R offers more error correction than CD-ROM
---- DVD-RAM offers more error correction than DVD+/-R
o Cheap backup media vs Magneto Optical
---- MO drive is 250$+, media is 5-8$+ for 1.3GB
---- DVD-RAM drive from LG is 90$+, media is 8$+ for 9.4GB
DVD-RAM is inherently more reliable than DVD+/-R as a
function of the phase-change media & error correction.
However, it isn't a bad idea to have 2 backup media available:
o Use HD for bulk data-backup
o Use DVD-RAM for duplication of critical data-backup
So perhaps the benefit of DVD-RAM is just that:
o As a backup drive sunk-cost is minimal
---- plenty of DVD-writers also write DVD-RAM (eg, LG Multi)
o It provides another media type
---- HDs do fail online & offline, online backups get deleted
---- HDs are vulnerable to shock, DVD-RAM order of magnitude better
Media quality does however matter:
o Consumer media does go through cash-cow to cash-dog
o At the cash-dog phase the production process seems to waver
o CD-ROM varies in quality, eventually single-layer DVD may too
o DVD-RAM may or may not, re usage in video recorders etc
o Magneto Optical in 3.5" did waver as it tried to compete on price
So as with all backup media:
o Don't pick one for 20yrs as you will fail
o Better to pick one which lasts for your purpose economically
o Then change / migrate as better technologies come along
If you want ultra-reliable, DLT seems to win out:
o Digital Linear Tape is derived from open reel
o It is not derived from consumer products like CDR, DVD, DAT etc
o Price of the smaller DLT drives is very good - below DAT now
o Reliability is good - but 1 backup media/drive is a 1 point of failure
Comes down to how much data, how often it changes, how important.
--
Dorothy Bradbury
www.dorothybradbury.co.uk for quiet Panaflo fans